Evaluating slag–metal deoxidation equilibrium in secondary steelmaking

Steel–slag reactions are important in steelmaking, in special in secondary steelmaking. Currently, desulfurization, deoxidation and inclusion removal are mostly performed during ladle refining. The extent to which these reactions proceed is governed by the initial state of the material reaching the ladle, the additions made to the ladle and by undesired interactions such as reoxidation and steel-refractory reactions. In this work, the extent to which equilibrium is approached for the different deoxidation reactions is Al-killed and Si–Mn deoxidized steel is evaluated using thermodynamics. These results are compared to measurements performed in industrial ladle furnaces. The comparisons make possible evaluating the efficiency of the deoxidation process. The results indicate that reoxidation by air caused by agitation probably play a key role on the ability to approach equilibrium, reaching low oxygen content in steel. It is also concluded that relatively long treatments with controlled agitation are needed to achieve steel–slag equilibrium.